The fuel flow check for N27AZ was performed on 30 March, 2022. The aircraft's main fuel tanks were drained until approximately three gallons remained in both right and left main tanks. Then, the aircraft was parked on the side of the taxiway with the tailwheel downhill, providing a deck angle of 19 degrees as recommended by users on the Bearhawk Forums. Flight testing will verify this angle.
The fuel supply line was disconnected from the carb and secured to an exhaust pipe nearby with the outlet at the same level as the carb inlet. A small table was configured to hold cans to catch gas as it ran through the fuel system.
To test the fuel flow, the fuel valve was placed in the desired position and the fuel was caught in a bucket until flow stabilized. Then, a timer was started and fuel was caught in an oil bottle for exactly 15 seconds. Four samples were taken at a time, then fuel flow was shut off and samples were weighed. All samples were very similar in weight. The sample shown in the picture contained 13.868 oz of fuel. This was converted to lbs per hour:
13.868 oz/(15 sec) x 4 / 16 (oz/lb) x 60 (min/hr) = 208 lb/hr
Fuel flow at max power is estimated using a 0.55 lb/hr/hp specific fuel consumption (this will be flight tested):
0.55 (lb/hr/hp) x 250 hp = 137.5 lb/hr
The final results of the fuel flow test in this configuration were"
208 lb/hr / 137.5 lb/hr = 1.51
Thus, the fuel system provides 151% of the fuel required at full power in this configuration.
The same test was conducted with the fuel selector in the Left and Right position. In each of these tests, fuel flow was 121% of the fuel required at max power. Thus, the aircraft will be placarded to takeoff, climb, and land with the fuel selector on BOTH.
The flow test was repeated with the fuel selector on BOTH until inadequate flow was measured at the outlet of the fuel line. At this point, there was 1.5 gal of fuel remaining in each tank. Therefore, each tank has an unusable fuel quantity of 1.5 gallons